It was late in the afternoon of an early September Saturday 70 years ago when the German bombers came, flying low, in formation, up the Thames, their engines roaring as they headed for London to start eight months of bombing the capital.

"It was the most amazing, impressive, riveting sight," wrote Colin Perry, a lad cycling that afternoon on Chipstead Hill, Surrey, in a memoir years later. "Directly above me were literally hundreds of planes … the sky was full of them. Bombers hemmed in with fighters, like bees around their queen, like destroyers round the battleship, so came Jerry."

Mavis Fabling, now 80, remembers that afternoon of 7 September 1940 just as clearly. She said: "I can still remember it very vividly. We lived in Abbey Wood, three miles from Woolwich Arsenal. My mother was baking in the kitchen, I was playing outside and my father was digging in the garden. Suddenly he rushed inside. He'd seen the planes overhead. 'Quick, quick, quick, get into the air raid shelter.' We ran down into the shelter in our garden.

"There were awfully frightening sounds, of bombs dropping and then there was one ghastly, thunderous sound. It was a direct hit on our neighbour's shelter. They were all killed, the whole family, except the father who was out. My mother had taken his wife shopping the day before to buy clothes at the Co-op. I can remember looking out of the window at the coffins being brought out and my mother very distressed.

"Then my father got the car from his work and took us down to my grandfather's house in Kent and I can remember looking back out of the window and seeing the sky glowing red behind us."

The records of the London fire brigade for that day, now kept in the metropolitan archives office in Clerkenwell, tell the story of the first major raid of the blitz in meticulous and sober detail. Neatly typed official green slips record each incident and a separate bound volume lists all the fires attended.

There had been scattered, small-scale raids for weeks, but this was the first concerted attack, ordered two days before by Hitler in retaliation for an RAF raid on Berlin a fortnight earlier.

The fire brigade's day started quietly enough but by late afternoon the records show, minute by minute, incidents coming thick and fast. First the East End, then the docks, both sides of the river, then the City and – more sporadically – the West End.

On Telegraph Hill, one of the highest points in south London, St Catherine's church was hit by an incendiary bomb: "Nave severely damaged and most part of roof off." It took 10 years before the church was rededicated. "We've just redone the rest of the roof," said the current vicar, Zambian-born Francis Makambwe. "So we're ready for another war."

The communities beside the docks got it worst: Silvertown on the north side was cut off for hours, its roads and terraces ablaze, Deptford too. At 6.07pm Childeric Road off New Cross Road was hit: 21 to 61 and 10-40 inclusive, 37 private houses severely damaged. At nearby Ruddigore Road, 13 private houses were damaged by explosion and fractured gas main. At Childeric Road today, the west side of the road still stands: a neat Victorian terrace of all the odd numbers. But the other side of the road is now a park.

Stacey Simkins, then 16 and an office boy enrolled as a fire brigade messenger – sometimes allowed to hold the hose when other firemen were busy – was off duty that night, at home with his family in East Ham. "When the bombers came over that night, most of us stood outside in the road, watching the fires down on the docks. It sounds ridiculous to say it now, doesn't it? We didn't think about the bombs, it was just that old cockney thing: 'Woss goin' on?' "

The fire brigade was nearly overwhelmed. At the start of the war, London had just 120 red fire engines and 2,000 motorised pumps. That night's records repeatedly say "Extinguished by handpump" or "Extinguished by strangers with sand."

Historian Francis Beckett, who has written a history of the fire brigade's union in the war, quotes one officer from the docks: "There were pepper fires loading the surrounding air heavily with stinging particles … so it felt like breathing fire itself; a paint fire, white-hot flame coating the pump with varnish. A rubber fire gave forth black clouds of smoke … sugar burns well in liquid form as it floats on the water.

"Tea makes a blaze that's sweet, sickly and intense. It struck one man as a quaint reversal of the fixed order of things to be pouring cold water on to hot tea leaves. A grain warehouse … brings forth banks of black flies, rats in hundreds and the residue of burnt wheat, a sticky mess that pulls your boots off."

By 6.30pm there were nine fires out of control in the docks. Timber stacks on Surrey docks were so fiercely alight that a fireboat had its paint scorched off in seconds. A rum warehouse went up, its contents spilling into the water and setting the Thames ablaze "like a Christmas pudding". There was a 1,000-metre wall of flame below Tower Bridge.

At 8.30pm, a second wave of bombers arrived, using the fires to guide them up the river. By 3am the next day, the exhausted firemen were gaining control. At 5am the all-clear was sounded.

The first night's raid left 430 killed, including seven firefighters, 60 boats sunk and the docks destroyed. Beckett quotes a fireman: "A man who returned from leave the following day found colleagues in shock, convinced they would not live for more than another week. Men who were old enough to have fought in the first world war said the western front offered nothing worse than they had seen."

The next night, the bombers came again, killing another 400. On 9 September 200 bombers came by day, 170 by night and their bombs killed 370. They came for 57 consecutive nights between mid-September and mid-November and then regularly for another six months until May 1941. Two years later, there would be doodlebugs and V2 rockets.

"Somehow, we just carried on," said Mavis Fabling. "I think it was worse for our parents than for us. I got used to doing my homework in the shelter. The teachers still expected you to learn your Shakespeare sonnet for the morning."